1. Field of the Invention
The present invention relates to camera positioning systems and, more specifically, to a camera positioning system using antagonistic actuators.
2. Description of the Related Art
The human eye enables the brain to perceive large amounts of information quickly, yet not all regions of space are perceived equally. Objects near the gaze direction, or fovea, receive the most attention, a lesser amount of information is gathered about objects in the remainder of the field of view, and some objects are out of the field of view and are not perceived. In this way, the brain is not overwhelmed by information that is not of interest. Because the area of interest may change rapidly, the eye can be reoriented with astounding performance by lightweight recti muscles. The recti muscles are contractile, compliant actuators that are activated in discrete steps by neural impulses.
The human eyeball, or globe, is oriented by means of antagonistic pairs of recti and oblique muscles. The range of achievable orientations follows Donders' Law and Listing's law, both for saccadic motion and smooth pursuit. Antagonistic pairs of contractile actuators with insertion points into the globe are an important part of the eye's kinematics. In actuality, eye muscles consist of a finite number of on-off motor units, or collection of muscle fibers innervated by a particular motor neuron. Cytoskeletal tissue couples the active acto-myosin filaments to the load. It is believed that this property allows muscles to function well in unstructured environments, since the elasticity of the muscle tends to return to a stable equilibrium when perturbed. Muscles are controlled by recruitment, whereby the nervous system increases or decreases the number of motor units active to increase or decrease the amount of actuation. Each individual motor unit can only be on or off and it cannot be proportionally controlled.
Most camera positioners use heavy traditional servo-motors. One example employs a cable-driven mechanism that is actuated by traditional servomotors. A cable-driven eye may be able to enforce the eye's kinematics, but rigid servomotors do not actually follow the processes related to the neurological basis for natural eye motion. This is partly because servo-motors tend to introduce velocity saturations and backlash. The resulting movement lacks the bandwidth of an actual eye.
Therefore, there is a need for a camera positioning system the models natural eye movement.